Until now, the method comprising the step of oxidizing a corresponding cyclic phenol sulfide is known as the method for producing an oxidized cyclic phenol sulfide. Examples of oxidizing agents used for oxidation reaction include hydrogen peroxide, organic peroxides, peracids, halogen oxides, N-halogen compounds, halogen molecules, oxygen, ozone, a nitric acid, and inorganic oxides. Hydrogen peroxide, halogen molecules, and inorganic oxides such as sodium perborate are preferable among them. Though a preferable solvent varies depending on the kind of an oxidizing agent, it is proposed to use halogenated hydrocarbon solvents such as chloroform and dichloromethane; alcohols such as methanol and ethanol; acetonitrile; polar solvents such as an acetic acid and water, and the like. Further, it is also known that, if necessary, catalysts such as vanadium (V) oxide, sodium metavanadate (V), titanium trichloride, tungsten (VI) oxide and sodium phosphate can be used in oxidation reaction (refer to Patent Literature 1 and Non-patent Literatures 1-3, for example).
Meanwhile, as the method for producing the corresponding cyclic phenol sulfide, there are the method which comprises the steps of using a phenol compound, sulfur and an alkali metal reagent as raw materials and synthesizing them by heating (refer to Patent Literatures 2-4, and Non-patent Literature 4, for example), and the method which comprises the steps of using a chain phenol sulfide, sulfur and an alkali metal reagent as raw materials and synthesizing them by heating (refer to Patent Literatures 5-8, for example). In each case, the produced cyclic phenol sulfide is isolated by processes such as crystallization, filtration, purification and drying.
Therefore, when producing an oxidized cyclic phenol sulfide, a cyclic phenol sulfide is once taken as the intermediate, and then it is again poured in a reactor, and a reaction reagent(s) is added thereto to conduct the oxidation reaction and to produce an oxidized cyclic phenol sulfide.
In the method for producing a cyclic phenol sulfide which comprises the steps of using a phenol compound, sulfur and an alkali metal reagent as raw materials and synthesizing them by heating, thermal cost is high since the reaction is conducted at high temperature. Further, the method requires equipments for safely detoxifying byproduct hydrogen sulfide gas. In addition, isolation of a cyclic phenol sulfide by processes such as crystallization, filtration, purification and drying causes loss of products in each treatment process, and it also causes the decrease in work efficiency due to the increase in operation time. Thus, it is costly to produce a cyclic phenol sulfide, and it makes a cyclic phenol sulfide expensive. Consequently, the production cost of an oxidized cyclic phenol sulfide which is the end product is much higher. It has been expected to find, as an effective cost improvement plan, a method for producing an oxidized cyclic phenol sulfide which comprises the steps of producing a cyclic phenol sulfide in the first reaction, and conducting thereto oxidation reaction which is the second reaction, without requiring various processes before said next reaction process and without various materials required for conducting the various processes together with improving work efficiency.
Patent Literature 1: WO 98/09959
Patent Literature 2: JP 9-227553 A
Patent Literature 3: JP 10-081681 A
Patent Literature 4: JP 2002-193963 A
Patent Literature 5: JP 10-081680 A
Patent Literature 6: JP 11-049770 A
Patent Literature 7: JP 2000-273096 A
Patent Literature 8: JP 2002-255961 A
Non-patent Literature 1: TETRAHEDRON LETTERS 39 (1998) 7559-7562
Non-patent Literature 2: TETRAHEDRON 57 (2001) 5557-5563
Non-patent Literature 3: J. Chem. Soc., Chem. Commun., 1998, 1345
Non-patent Literature 4: H. Kumagai et al., Tetrahedron Lett. (1997), 38, 3971-3972